理论上来说多台宿主机之间的docker容器之间是无法通讯的，但是多台宿主机之间的docker容器之间是可以通讯的，主要是通过VXLAN技术来实现的。
GitHub上对于docker-overlay-network的介绍。
17.1 overlay网络和etcd实现多机容器通信
docker在创建容器的时候默认会使用bridge网络，要实现多机容器间通信，需要使用overlay网络，但是要实现多机的容器通信，通信的两个容器的IP肯定不能一样，所以我们需要借助第三方的工具来实现。这里使用ectd。
安装etcd
在第一台服务器上安装
[root@docker ~]# wget https://github.com/coreos/etcd/releases/download/v3.0.12/etcd-v3.0.12-linux-amd64.tar.gz
[root@docker ~]# tar xf etcd-v3.0.12-linux-amd64.tar.gz
[root@docker ~]# cd etcd-v3.0.12-linux-amd64/
[root@docker ~]# nohup ./etcd --name docker-node1 --initial-advertise-peer-urls http://192.168.205.10:2380
--listen-peer-urls http://192.168.205.10:2380
--listen-client-urls http://192.168.205.10:2379,http://127.0.0.1:2379
--advertise-client-urls http://192.168.205.10:2379
--initial-cluster-token etcd-cluster
--initial-cluster docker-node1=http://192.168.205.10:2380,docker-node2=http://192.168.205.11:2380
--initial-cluster-state new&
[root@docker ~]#
在第二台服务器上安装
[root@docker ~]# wget https://github.com/coreos/etcd/releases/download/v3.0.12/etcd-v3.0.12-linux-amd64.tar.gz
[root@docker ~]# tar xf etcd-v3.0.12-linux-amd64.tar.gz
[root@docker ~]# cd etcd-v3.0.12-linux-amd64/
[root@docker ~]# nohup ./etcd --name docker-node2 --initial-advertise-peer-urls http://192.168.205.11:2380
> --listen-peer-urls http://192.168.205.11:2380
> --listen-client-urls http://192.168.205.11:2379,http://127.0.0.1:2379
> --advertise-client-urls http://192.168.205.11:2379
> --initial-cluster-token etcd-cluster
> --initial-cluster docker-node1=http://192.168.205.10:2380,docker-node2=http://192.168.205.11:2380
> --initial-cluster-state new&
[root@docker ~]#
检查cluster状态
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl cluster-health
member 21eca106efe4caee is healthy: got healthy result from http://192.168.205.10:2379
member 8614974c83d1cc6d is healthy: got healthy result from http://192.168.205.11:2379
cluster is healthy
重启docker服务
在第一台服务器上重启
systemctl stop docker.service
/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock --cluster-store=etcd://192.168.205.11:2379 --cluster-advertise=192.168.205.11:2375&
在第二台服务器上重启
systemctl stop docker.service
/usr/bin/dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock --cluster-store=etcd://192.168.205.10:2379 --cluster-advertise=192.168.205.10:2375&
创建overlay network
在其中任意一台服务器上创建一个overlay网络
[root@docker ~]# docker network create -d overlay demo
[root@docker ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
038cb815ca11 bridge bridge local
efeabebb2ed5 demo overlay global
674c97014876 host host local
ac706f4efd8e none null local
[root@docker ~]# docker network inspect demo
[
{
"Name": "demo",
"Id": "efeabebb2ed5b63e705cb2eb3b9f77109119a71fdb89d05b105db30ae25c06f6",
"Created": "2018-06-06T09:50:59.567617763Z",
"Scope": "global",
"Driver": "overlay",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "10.0.0.0/24",
"Gateway": "10.0.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {},
"Labels": {}
}
]
[root@docker ~]#
另一台服务器上的overlay网络也会被同步创建。这都是由etcd实现的：
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls
/docker
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker
/docker/nodes
/docker/network
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker/nodes
/docker/nodes/192.168.205.10:2375
/docker/nodes/192.168.205.11:2375
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker/network
/docker/network/v1.0
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker/network/v1.0
/docker/network/v1.0/endpoint_count
/docker/network/v1.0/endpoint
/docker/network/v1.0/ipam
/docker/network/v1.0/idm
/docker/network/v1.0/overlay
/docker/network/v1.0/network
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker/network/v1.0/overlay
/docker/network/v1.0/overlay/network
[root@docker etcd-v3.0.12-linux-amd64]# ./etcdctl ls /docker/network/v1.0/overlay/network
/docker/network/v1.0/overlay/network/efeabebb2ed5b63e705cb2eb3b9f77109119a71fdb89d05b105db30ae25c06f6
[root@docker etcd-v3.0.12-linux-amd64]#
分别在两胎服务器上创建容器
在第一台服务器上创建
[root@docker ~]# docker run -d --name test1 --net demo busybox sh -c "while true; do sleep 3600; done"
[root@docker ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
170e8edf81f2 busybox "sh -c 'while true; …" 3 minutes ago Up 3 minutes test1
[root@docker ~]# docker exec -it test1 ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
13: eth0@if14: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue
link/ether 02:42:0a:00:00:02 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.2/24 brd 10.0.0.255 scope global eth0
valid_lft forever preferred_lft forever
15: eth1@if16: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
link/ether 02:42:ac:12:00:02 brd ff:ff:ff:ff:ff:ff
inet 172.18.0.2/16 brd 172.18.255.255 scope global eth1
valid_lft forever preferred_lft forever
[root@docker ~]#
在第二台服务器上创建
[root@docker ~]# docker run -d --name test2 --net demo busybox sh -c "while true; do sleep 3600; done"
[root@docker ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8b50c21f1337 busybox "sh -c 'while true; …" 2 minutes ago Up 2 minutes test2
[root@docker ~]# docker exec -it test2 ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
7: eth0@if8: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue
link/ether 02:42:0a:00:00:03 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.3/24 brd 10.0.0.255 scope global eth0
valid_lft forever preferred_lft forever
10: eth1@if11: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
link/ether 02:42:ac:12:00:02 brd ff:ff:ff:ff:ff:ff
inet 172.18.0.2/16 brd 172.18.255.255 scope global eth1
valid_lft forever preferred_lft forever
[root@docker ~]#
查看demo网络信息：
[root@docker ~]# docker network inspect demo
[
{
"Name": "demo",
"Id": "efeabebb2ed5b63e705cb2eb3b9f77109119a71fdb89d05b105db30ae25c06f6",
"Created": "2018-06-06T09:50:59.567617763Z",
"Scope": "global",
"Driver": "overlay",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "10.0.0.0/24",
"Gateway": "10.0.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"170e8edf81f2bc216b926c52928c0e6977809387cc21db433c56d7b7d397f49b": {
"Name": "test1",
"EndpointID": "247454410f441b545c97c3d53cae508cbdbb9c2d91745381adf70580a77f8ec7",
"MacAddress": "",
"IPv4Address": "10.0.0.2/24",
"IPv6Address": ""
},
"ep-5e95b84eff1dbb3fbdc6abb4daa0707e117dac66220222a2e22a75bf6b7eb09d": {
"Name": "test2",
"EndpointID": "5e95b84eff1dbb3fbdc6abb4daa0707e117dac66220222a2e22a75bf6b7eb09d",
"MacAddress": "",
"IPv4Address": "10.0.0.3/24",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {}
}
]
[root@docker ~]#
测试两个容器间能否通信
[root@docker ~]# docker exec -it test1 ping 10.0.0.3
PING 10.0.0.3 (10.0.0.3): 56 data bytes
64 bytes from 10.0.0.3: seq=0 ttl=64 time=3.251 ms
64 bytes from 10.0.0.3: seq=1 ttl=64 time=0.693 ms
64 bytes from 10.0.0.3: seq=2 ttl=64 time=0.591 ms
64 bytes from 10.0.0.3: seq=3 ttl=64 time=0.579 ms
64 bytes from 10.0.0.3: seq=4 ttl=64 time=0.776 ms
^C
--- 10.0.0.3 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 0.579/1.178/3.251 ms
[root@docker ~]#
[root@docker ~]# docker exec -it test1 ping test2
^C[vagrant@docker-node1 ~]$ docker exec -it test1 ping test2
PING test2 (10.0.0.3): 56 data bytes
64 bytes from 10.0.0.3: seq=0 ttl=64 time=1.024 ms
64 bytes from 10.0.0.3: seq=1 ttl=64 time=0.565 ms
64 bytes from 10.0.0.3: seq=2 ttl=64 time=0.806 ms
64 bytes from 10.0.0.3: seq=3 ttl=64 time=0.597 ms
64 bytes from 10.0.0.3: seq=4 ttl=64 time=0.498 ms
^C
--- test2 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 0.498/0.698/1.024 ms
[root@docker ~]#
[root@docker ~]# docker exec -it test2 ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: seq=0 ttl=64 time=3.374 ms
64 bytes from 10.0.0.2: seq=1 ttl=64 time=0.531 ms
64 bytes from 10.0.0.2: seq=2 ttl=64 time=0.499 ms
^C
--- 10.0.0.2 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.499/1.468/3.374 ms
[root@docker ~]#
[root@docker ~]# docker exec -it test2 ping test1
PING test1 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: seq=0 ttl=64 time=0.685 ms
64 bytes from 10.0.0.2: seq=1 ttl=64 time=0.754 ms
64 bytes from 10.0.0.2: seq=2 ttl=64 time=0.642 ms
64 bytes from 10.0.0.2: seq=3 ttl=64 time=1.080 ms
^C
--- test1 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 0.642/0.790/1.080 ms
[root@docker ~]#